For infrared spectrophotometer it is interesting to combine functions like dispersion and focusing in one optical element, a diffractive optical element (DOE).
The state of the art of design techniques for DOEs focuses on the coherent illumination case, which corresponds to a monochromatic point source. In this case the function of the DOE can be analyzed for one wavelength e.g. using scalar wave field propagation based on the Rayleigh-Sommerfeld-Integral. Often infrared photometers use a thermal...